Macros Calculator (Cutting / Bulking)
Getting your macros right is the difference between spinning your wheels and making consistent progress. This calculator takes your Total Daily Energy Expenditure (TDEE) — either entered directly or computed from your BMR and activity level — applies a calorie adjustment for your goal (cut −20%, maintain, or lean bulk +10%), then splits those calories into protein, fat, and carbohydrates using evidence-based ranges. No guesswork, just numbers.
When to use this calculator
- Planning a cut phase while preserving lean muscle mass
- Setting up a lean bulk with a controlled 10% calorie surplus
- Recalculating macros after a weight change or training block shift
- Comparing macro splits before starting a new diet protocol
- Verifying that a coach-prescribed plan aligns with evidence-based ranges
- Estimating daily food targets when switching from IIFYM to a structured meal plan
How it works
2 min readWhat is a Macro Calculator?
A macro calculator determines your daily protein, carbohydrate, and fat targets based on your TDEE and fitness goal. It applies calorie adjustments—typically −20% for cutting or +10% for bulking—then distributes those calories across macronutrients using evidence-based ratios. Most active adults need 1.6–2.2 g protein per kg bodyweight for optimal body composition changes.
How It Works
This calculator follows a four-step process:
Step 1 — Determine TDEE
If you enter your TDEE directly, that value is used as-is. If you choose BMR + activity, the calculator uses the Mifflin–St Jeor equation (the most accurate general-population equation per a 2005 meta-analysis in the Journal of the American Dietetic Association):
Male: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Female: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161TDEE = BMR × activity multiplier:
| Activity Level | Multiplier |
|---|---|
| Sedentary | 1.2 |
| Lightly active | 1.375 |
| Moderately active | 1.55 |
| Very active | 1.725 |
| Extra active | 1.9 |
Step 2 — Apply calorie goal adjustment
target_kcal = TDEE × 0.80 (−20%)target_kcal = TDEE × 1.00target_kcal = TDEE × 1.10 (+10%)A 20% deficit is the upper bound of aggressive-but-safe cutting per sports nutrition literature. A 10% surplus is sufficient for lean muscle accrual without excessive fat gain.
Step 3 — Set protein grams
Protein is anchored to bodyweight, not calories, to protect lean mass:
protein_g = weight_lb × protein_multiplierDefault is 1.0 g/lb (≈2.2 g/kg), the upper end of the evidence-based range from the International Society of Sports Nutrition (ISSN) Position Stand. Protein provides 4 kcal/g.
Step 4 — Allocate fat, then fill carbs
fat_g = (target_kcal × fat_pct) / 9 // fat = 9 kcal/g
fat_kcal = fat_g × 9
protein_kcal = protein_g × 4
carbs_kcal = target_kcal − protein_kcal − fat_kcal
carbs_g = carbs_kcal / 4 // carbs = 4 kcal/gIf carbs_g comes out negative (protein + fat exceed target calories), the calculator caps protein at the target calories minus minimum fat allocation and notes the conflict.
Worked Example
180 lb male, 5'10", 30 years old, moderately active, cutting with default settings:
Split: ~33% protein / 27% fat / 40% carbs.
Limitations
Frequently asked questions
What is TDEE and why does it matter?
Total Daily Energy Expenditure (TDEE) is the total number of calories you burn in a day, including your basal metabolic rate (BMR) plus all physical activity. It is the baseline from which any calorie surplus or deficit is calculated. Without an accurate TDEE, your macro targets will be off.
Why is the default protein set at 1.0 g per lb of bodyweight?
1.0 g/lb (≈2.2 g/kg) is the upper bound of the range consistently supported by sports nutrition research for muscle retention during a caloric deficit. It leaves a safety margin and is practical for most people tracking macros.
Can I lose fat and build muscle at the same time (body recomposition)?
Yes, but primarily in beginners, detrained individuals, or people returning from a layoff. For them, maintaining calories near TDEE with high protein (1.0 g/lb) and progressive resistance training can drive simultaneous fat loss and muscle gain. Experienced lifters generally need distinct cut and bulk phases.
Why is a 20% deficit chosen for cutting?
A 20% deficit is large enough to produce meaningful fat loss (roughly 0.5–1% of bodyweight per week for most people) while being sustainable and limiting muscle loss when protein is kept high. Deeper cuts (>25–30%) increase muscle loss risk and hormonal disruption.
Why only a 10% surplus for bulking?
The body can only synthesize a limited amount of new muscle tissue per week (roughly 0.25–0.5 lb for men, less for women). A 10% surplus provides enough extra energy to maximize muscle protein synthesis without accumulating excessive body fat — a hallmark of 'lean bulking.'
What if my carbs come out very low or negative?
This happens when protein and fat combined exceed your calorie target — most commonly in very short cuts with high protein intakes. The calculator will flag it. Solutions: lower your protein multiplier slightly (0.8 g/lb is still evidence-based), reduce fat to 25%, or accept a less aggressive deficit.
How accurate is the Mifflin–St Jeor equation?
Mifflin–St Jeor predicts measured RMR within 10% for roughly 82% of the population, making it the most accurate widely-used predictive equation per a 2005 JADA meta-analysis. Athletes with high muscle mass may find it slightly underestimates BMR; obese individuals may find it slightly overestimates.
Should I track macros in grams or just calories?
Both matter, but grams give you a more actionable target. Hitting your calorie target but falling short on protein (e.g., only 100 g/day during a cut) will cost you more muscle mass than a slight calorie overage with full protein met.
How often should I recalculate my macros?
Recalculate every 4–6 weeks, or whenever your bodyweight changes by more than 5 lb (≈2.3 kg). As you lose or gain weight, your BMR shifts, so your TDEE and macro targets need updating to stay accurate.
Do these macros apply to vegetarians or vegans?
The calorie and macro targets are the same regardless of diet type. However, plant-based protein sources often have lower leucine content and digestibility, so some researchers suggest adding 10–20% to the protein target for those relying entirely on plant protein.